Question

Q1. Phosphocreatine

Select one:
a) provides the muscle cell with a quick energy source
b) removes Ach from the neuromuscular junction
c) blocks the myosin binding site in a relaxed muscle
d) responsible for the release of Ach
e) pumps Ca2+ back into the sarcoplasmic reticulum

Q2. In twitch summation,

Select one:
a) the muscle fiber is stimulated again before the filaments have completely returned to their resting position
b) stronger muscle contractions occur but stronger action potentials do not uoccur
c) a second action potential occurs in the muscle fiber, before the first action potential is finished
d) both a and b are correct
e) all of the above are correct

Q3. The force generated by a single muscle fiber:

Select one:
a) is always the same
b) can be increased by increasing the frequency of action potentials
c) can be increased by motor unit recruitment
d) more than one of the above is correct

Answer 1

1.  Phosphocreatine - Option A i.e. provides the muscle cell with a quick energy source.

Phosphocreatine is a molecule that has the ability to store energy in its phosphate bonds. When the muscle is in resting state, ATP converts it's energy into phosphocreatine and ADP. This is then stored and used whenever energy is required.

2.In twitch summation - Option E i.e. all the options are correct

Muscle twitch is small muscle contractions which occurs due to stimulation of the nerve that innervates it. Twitch summation is adding of second twitch. Summation increases the force of contraction by increasing the frequency of the stimulus to the muscle fibers. All the 3 options i.e a,b and c are correct.

3. The force generated by a single muscle fiber - Option D i.e. more than one of the above is correct. Here option B and C are correct

The force generated by a single muscle fibers can be increased by increasing the frequency of action potentials
and can be increased by motor unit recruitment